Solid-source diffused junction for fin-based electronics

ABSTRACT

A solid source-diffused junction is described for fin-based electronics. In one example, a fin is formed on a substrate. A glass of a first dopant type is deposited over the substrate and over a lower portion of the fin. A glass of a second dopant type is deposited over the substrate and the fin. The glass is annealed to drive the dopants into the fin and the substrate. The glass is removed and a first and a second contact are formed over the fin without contacting the lower portion of the fin.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a U.S. National Phase Application under 35U.S.C. §371 of International Application No. PCT/US2014/046525, filedJul. 14, 2014, entitled SOLID-SOURCE DIFFUSED JUNCTION FOR FIN-BASEDELECTRONICS.

FIELD

The present disclosure relates to Fin-based electronics and, inparticular to junctions using solid source diffusion.

BACKGROUND

Monolithic integrated circuits typically have a large number oftransistors, such as metal-oxide semiconductor field-effect transistors(MOSFETs) fabricated over a planar substrate, such as a silicon wafer.System-on-a-chip (SoC) architectures use such transistors in both analogand digital circuitry. When high-speed analog circuitry is integrated onas single monolithic structure with digital circuitry, the digitalswitching can induce substrate noise that limits the precision andlinearity of the analog circuitry.

Junction gate field effect transistors (JFETs) are used primarily inanalog applications due to the superior low noise performance they offercompared to standard MOSFET (Metal Oxide Semiconductor FET) devices.JFETs are useful in radio frequency devices such as filters andequalizers and also in power circuits for power supplies, powerconditioners and the like.

JFET transistors are fabricated in the hulk of a planar processtechnology using implanted junctions to establish a back-gate, channel,and top-gate electrodes. The JFET is made using implanted n and p-typewells to form the top and back gates, as well as the source and draincontacts. This bulk planar process may be replaced for MOSFET devicesusing fins formed on the substrate. The formation of FET devices on finshas been referred to as a FinFET architecture.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich like reference numerals refer to similar elements.

FIGS. 1-4 are cross-sectional side view and corresponding front viewdiagrams of a p-channel current flow control gate on a fin architectureaccording to an embodiment of the invention.

FIG. 5 is a cross-sectional side view diagram of an n-channel currentflow control gate on fin architecture according to an embodiment of theinvention.

FIG. 6 is a cross-sectional side view diagram of a p-channel currentflow control device with multiple gates on fin architecture according toan embodiment of the invention.

FIGS. 7-22 are cross-sectional side view and corresponding front viewdiagrams of stages of fabrication for the device of FIG. 1 according toan embodiment of the invention.

FIGS. 23-28 are cross-sectional side view and corresponding front viewdiagrams of alternative stages of fabrication for FIGS. 13-22 accordingto an embodiment of the invention.

FIG. 29 is a cross-sectional side view diagram of a transistor on afinFET architecture according to an embodiment of the invention.

FIG. 30 is a circuit diagram of the transistor of FIG. 29 according toan embodiment of the invention.

FIGS. 31-55 are cross-sectional side view and corresponding front viewdiagrams of alternative stages of fabrication of the transistor of FIG.29 according to an embodiment of the invention.

FIG. 56 is a block diagram of a computing device incorporating anintegrated circuit built with a FinFET architecture and including asolid source diffused junction according to an embodiment

DETAILED DESCRIPTION

A high performance JFET may be fabricated on a fin of a FinFET processarchitecture. Because the electrical characteristics of a JFET rely onits structure as a bulk-transport device, a JFET device built on a finin the same way as a MOSFET device loses its bulk transport and highcurrent capabilities. A JFET can be built, however, using solid-sourcediffusion on a fin architecture to obtain a high-performance, scalabledevice for system-on-chip process technologies.

A similar technique may be used to form a variable resistor. A p-channelor n-channel may be formed in a fin with a contact on either side. Acontrol gate may be formed over the channel in the fin between the twocontacts. Due to the nature of current conduction inside of the fin andthe narrow width of the fin, the control gate provides excellentelectrostatic control of the carrier density inside the fin. By usingthis control gate, the carrier density can be increased (through channelaccumulation) or decreased (though channel depletion) depending on thebias applied.

The same control gate technique may also be used on one or both sides ofthe gate of a JFET in a fin. The control gates act as a variableresistor built into the fin-based JFET architecture. As JFETs aretypically longer channel devices to sustain high voltage operation,these control gates have no added layout area penalty and may improvethe pinch-off voltage needed to fully shut off the channel.

FIG. 1 is a cross-sectional side view diagram of a current flow controlgate in FinFET architectures. It shows a portion of a fin on a substratein a FinFET architecture. The fin 106, 108 protrudes from the substrate102 which is covered in an isolation oxide 104. A device 101 is built onthe substrate 102 and the fin. An n-well 106 is formed on the fin andmay extend partially into the substrate and a p-type channel 108 hasbeen formed over the n-well on the fin. The fin as shown is made up ofthese two parts, however, the fin may extend beyond the device andbeyond the n-well and the p-channel on either side of the device. A pairof contacts 110, 112 is formed in the p-channel, one on each side of thechannel. A control gate 114 is formed between the two contacts over thefin. Current flow from one channel contact 110 to the other channelcontact 112 through the p-channel 108 is controlled by the control gate114.

A part of the device 101 of FIG. 1 is shown in the cross-sectional frontview diagram of FIG. 2. This view is taken as a cross-section throughthe control gate 114, through the line 2-2 of FIG. 1. As shown, theisolation oxide 102 and the n-well 106 are directly over the substrate102. The p-channel 108 is formed over the n-well 106.

The control gate 114 is formed over and around the p-channel surroundingit on three sides. This allows the control gate to electrically pinchcarrier flow through the p-channel between the two contacts 110, 112.The p-channel is surrounded by as barrier layer 118 between thep-channel and the control gate to prevent diffusion between thep-channel and the gate.

The n-well extends through the isolation oxide. The n-well also extendsabove and below the top of the isolation oxide 104. This allows thecontrol gate to extend all the way around the p-channel to moreeffectively control carrier flow through the p-channel. As shown, thecontrol gate extends deeper on the fin than does the p-channel. Thisensures that the p-channel is more than completely enclosed on threesides. Alternatively, the gate may be made smaller to allow a leakagecurrent through the p-channel even when the maximum voltage has beenapplied to the control gate.

FIG. 3 is a cross-sectional front view diagram of the fin and device 101of FIG. 1 taken through either one of the two contacts 110, 112 and inthis example through line 3-3 of FIG. 1. As shown, the n-well is deepthrough the isolation oxide 104 to the substrate 102. The contact isformed over the p-channel 108 to provide a suitable connection from anexternal source to the p-channel. The contact does not extend over then-well and is not as deep as the control gate 114. Electrodes 120 and122 are formed on the two contacts 110, 112 so that a current may beapplied to one or the other of the two contacts. The current flowbetween the two contacts is then controlled by the control gate.

FIG. 4 is a cross-sectional front view diagram of an alternative contact110-1. FIG. 4 presents the same view as FIG. 3 but for an alternativeembodiment. The contact of FIG. 4 may be formed by adding an isolationoxide 124 to the contact of FIG. 3. The same isolation oxide 104 andn-well 106 are formed over a substrate 102 such as a silicon substrate.The p-channel 108 is built over the n-well 106 and the top is coveredwith a contact 110, 126, similar to the contact 110 of FIG. 3. In theexample of FIG. 4 an additional fin spacer 124 is applied between theisolation oxide and the contact 126 to prevent diffusion from betweenthe n-well and the p-type contact. In practice, the fin is first formedand then doped to form an n-well and p-channel. The fin spacer 124 isthen built up around the fin with the doped contact 126 over it.

FIG. 5 is a cross-sectional side view diagram of an n-channel variablecurrent flow device in FinFET architecture. It shows an alternativevariable resistor device 200 in which an n-channel is used instead of ap-channel. In this example no substrate is shown for simplicity,however, the device is formed using a FinFET architecture similar to thedevice of FIG. 1. A fin is built up over the substrate. The fin is dopedto form a deep p-well 206. The fin is surrounded by an isolation oxide204. The upper part of the fin is doped to form art n-channel 288 abovethe p-well 206.

A pair of contacts, in this case n-type contacts 210, 222, is formed onecontact on either side of the n-channel. Electrodes 220, 224 areattached to the contacts to allow a current to be applied to one of thecontacts. Flow through the n-channel 208 is controlled by a control gate214 which has an electrode 230 to which a variable voltage may beapplied. The variable resistor 200 of FIG. 2 operates similarly to thevariable resistor 101 of FIG. 1. An increasing voltage applied to theterminal 230 allows more current to flow through the n-channel by thecontrol gate 214. In this case, the current is in the form of electronsrather than holes, however, the fundamental operation is the same.

FIG. 6 is a cross-sectional side view diagram of a p-channel device withvariable current flow controlled by multiple gates in FinFETarchitecture. P-type contacts 310, 312 as in FIG. 2 are combined with ann-type contact 318 to make a double gated p-type device 300. This devicehas a fin with a deep n-well 306. The upper part of the fin is doped asa p-channel 308 and the fin is surrounded by an isolation oxide 304.P-type contacts 310, 312 are formed at either end of the p-channel. Ann-type contact 318 is formed between the two p-type channels. A firstcontrol gate 314 is placed between the left side p-type contact 310 andthe center n-type contact 318. A second control gate 316 is placedbetween the n-type contact 318 and the right side p-type contact 312.The three contacts 310, 312, 318 each have a terminal 320, 324, 322 towhich a current may be applied. The two control gates 314, 316 also haveterminals 326, 328 to which a voltage may be applied. By controlling thevoltage in one or both of the control gates, the current flow throughthe p-channel may be regulated. In addition, the n-type contact 318 mayalso be used to regulate current flow through the device 300. This threecontact device allows for a very precise control of current flow whichmay be used for any of a variety of different purposes.

As shown in FIGS. 1-6, a variety of different devices may be formedusing a fin architecture and solid surface annealing. The most simpledevice has a contact at each end of a current channel. The contacts canbe coupled to an electrode or another device. This supplies an isolatedelectrical conduit between two points. The structure can be augmented byone or more control gates as shown in FIGS. 1 and 6. The structure canbe augmented with transistor gates as shown in FIG. 29 or the device mayhave a combination of different types of gates. A variety of differenttypes of transistor, resistor, and other current control devices can beformed using the techniques described herein.

FIGS. 7-28 are cross-sectional side view diagrams and correspondingfront view diagrams of stages of fabrication for a variable resistordescribed, for example, in FIGS. 1 and 5. In FIGS. 7 and 8 a substrate402 such as a silicon substrate has been processed so that it has a fin404 while only one fin is shown, typically a substrate will have manyhundreds of fins or thousands depending upon the intended application.

In FIGS. 9 and 10 an n doped glass is deposited over the substrate. Then-type glass 406 contains a doped oxide and may be in the form, forexample, of a phosphosilicate. The glass may be applied by chemicalvapor deposition or a variety of other processes.

FIGS. 11 and 12 show that a spin-on hard mask 408 has been applied overthe substrate and the glass as a thick blanket coat. The mask covers thesubstrate and a lower part of the fin. The mask layer leaves only theupper part of the fin exposed. The glass on the rest of the structure iscovered. A blanket coat of such a blocking material, by protecting someareas and not others, allows additional layers to be appliedselectively.

In this case, as shown in FIGS. 13 and 14 the spin-on hard mask has beenused to protect the n-doped glass on the lower part of the fin and thesubstrate from an etch process. As a result, the n-doped glass appliedto the top of the fin has been removed. As shown in FIGS. 13 and 14, theexposed top of the fin sets the depth of the p-type channel which is tobe formed and also sets the back gate depth. In FIGS. 13 and 14 theglass over the upper part of the fin has been removed the carbon hardmask has been removed and a low doped p-type glass has been depositedover the entire structure.

In FIGS. 15 and 16 the structure of FIGS. 13 and 14 has been annealedand all of the glass has then been removed. The anneal drives thedopants from the glass into the silicon or other thin material. Theglass can then be removed using a standard oxide etching process or anyof a variety of other processes. As a result of the glass deposition andannealing, the structure of FIGS. 15 and 16 has a lower silicon portion402 with an n-type substrate area 412 and an n-type lower portion of thefin 414. Note that upper part of the substrate closest to the fin isalso doped due to the n-type glass that was deposited over thesubstrate. This allows a very deep n-well to be formed under thep-channel at the top part of the fin. The top of the fin 416 is doped asp-type to later form a p-channel over a deep n-well.

In this example, the doped glass forms a solid source of dopants. Thedopants are diffused into the fin from the solid source when thestructure is annealed. The particular process parameters of this solidsource diffusion may be adjusted to suit the particular materials, thedesired doping levels, and the overall process flow for fabricating thedevices. While doped glass is described other solid source diffusionmethods and technologies may be used depending on the particularapplication and process parameters.

In FIGS. 17 and 18 an isolation oxide 418 is applied, this isolationoxide may be any of a variety of oxides including silicon dioxide. Theoxide is then planarized in FIGS. 19 and 20 and patterned to allow apolysilicon control gate 420 structure to be applied over the fin. Thepolysilicon material may then be removed and backfilled with metal toform a metal control gate.

In FIGS. 21 and 22, contacts 420, 422 are applied over the fin and aspacer 426 is applied to separate the control gate 420 from the twocontacts 422, 424. The spacers may be formed by deposition and may beleft in place to control epitaxial growth which may be applied to thestructure in a later process.

As shown in FIGS. 19 and 20, the control gate surrounds the fin on threesides, the top and two vertical sides of the fin. Similarly, thecontacts 420, 422 also surround the fin on the top and both sides. As aresult the current flow from the contact through the p-channel ismaximized and the effect of the control gate on the p-channel is alsomaximized.

FIGS. 23 to 28 are side cross-sectional and corresponding front viewdiagrams of a stage of fabrication to show an alternative fabricationprocess. In the example of FIGS. 23 and 24, a deposition oxide has beenapplied over the structure of FIG. 4G. The structure of 4G has beenformed and this structure has then been annealed. However, instead ofthen removing the doped glass from the structure, an oxide isolationlayer 518 is applied over the fin, the substrate and the glass. As aresult of the anneal, a portion 512 of the silicon substrate 502 isn-doped, portion of the fin 514 and the substrate 512 forms the deepn-well with a more highly doped p-type channel 516 on the upper part ofthe fin. Due to the oxide isolation structure, the p-doped glass 510covers the fin and the n-type glass 506 covers the fin and thesubstrate.

In FIGS. 25 and 26 the deposited oxide 518 has been planarized andremoved down to is below the n-well area or the start of the n-typeportion of the fin 514. This exposes most of the fin. All of thedeposited glass above the oxide layer 518 is then removed and apolysilicon structure 520 is formed over and around the fin to start thefabrication of the control gate.

In FIGS. 27 and 28 the control gate has been formed, the extra oxide hasbeen removed, and the device is in a preliminary stage ready forapplication of the contacts as shown in FIGS. 21 and 22. By applying theisolation oxide before removing the deposited glass layers, severalsteps in the fabrication process may be avoided, reducing costs.

FIG. 29 is a cross-sectional side view diagram of a transistor deviceformed on a fin of a FinFET architecture. As described above,solid-source diffusion may be used along with implantation to formcontacts for a resistor. The same techniques may be used for the source612, drain 614, and top back-gate contacts 626, 628 of a JFET. In a JFET600 as shown in FIG. 29, current flows from a p-type source 612 to ap-type drain 614 through, in this case, a p-type channel 616 when a gate620 between the source and drain is off. The p-channel, the source, gateand drain are all formed in a fin 622 of a FinFET device architecture.The n-type gate has a contact 624 that is also coupled to an n-type topgate 626 and a back gate 628 that are also formed on the finelectrically coupled to the p-channel but spaced apart from the source,gate, and drain.

As the gate voltage is increased, the n-type back 626 and top 620 gatesdeplete the narrow p-channel of carriers in between the source and thedrain. This pinches off the channel and reduces the current that canflow from the source to the drain. A similar design may be applied to ann-type channel in a fin with an n-type source and drain and a p-typegate.

Using a fin-based architecture additional control gates 630, 632 similarto the control gate of the variable resistor described herein may beused to further enhance or retard current flow through the p-channel.The control gates may be formed inside the JFET on one or both sides ofthe gate. Similar to the variable resistor of FIG. 1, the control gatesof FIG. 29 are fabricated over the fin covering the fin on the top andon two sides to substantially surround the p-channel.

Due to the nature of current conduction inside of the fin and the narrowwidth of the fin, the three sided enclosure of the gate enablesexcellent electrostatic control of the carrier density inside the fin.The control gate is able to alternately increase the carrier densitythrough channel accumulation and decrease the carrier density thoughchannel depletion depending on the bias applied. As described above, inthis way the control gates are acting as a variable resistor built in tothe fin-based WET architecture. As JFETs are typically longer channeldevices to sustain high voltage operation, these control gates typicallyhave no added layout area penalty and improve the pinch-off voltageneeded to fully shut off the channel.

FIG. 30 shows a corresponding circuit representation of the FinFETtransistor showing the gate 620 to control current flow from the source612 to the drain 614 and connections for the two control gates 630, 632.

An example process sequence on a 14 nm like technology is illustratedbelow. Standard processing is used to define the fins, and an n-typeglass is subsequently deposited on top of the fins conformally. Theglass is patterned using, for example a spin-on hardmask recessed toexpose the top of the fins. A conformal p-type glass is then deposited.An anneal is performed to drive in the dopants from the glass into thesilicon fins, and the glass is subsequently removed. Standard isolationoxide is deposited, planarized, and recessed to set the active finheight. The midsection gate spacers are then deposited.

In some embodiments, the spacer is completely or partially left on thefin to enable downstream epitaxial patterning of the JFET device.Epitaxial silicon undercut etch and growth may then be performed usingconventional techniques and the gate isolation oxide may then bedeposited to enable contact formation. The contacts for the source,drain, and gates are then constructed.

FIGS. 31-55 are cross-sectional side and front view diagrams of stagesof fabrication of a JFET in a FinFET architecture. In FIGS. 31 and 32 asubstrate 702 has one or more fins 704 formed on it. The fin may beformed in any of a variety of different ways depending on the particularimplementation. In FIGS. 33 and 34 an n-type glass 706 is deposited overthe fin and substrate. This glass may be formed by a variety ofdifferent deposition processes and contains a moderate dopantconcentration of n-type dopant. As mentioned above borosilicate orphosphosilicate may be applied by chemical vapor deposition or any othertechnique may be used.

In FIGS. 35 and 36 a blocking material 708, such as a planarizingspin-on hard mask is applied and patterned over the substrate. In theillustrated example a thick blanket is used so that the top of the finis exposed while the bottom of the fin and the top of the substrate arecoated. The height of the mask layer determines the depth of thep-channel.

In FIGS. 37 and 38 the n-type glass has been removed where it isexposed, that is where it is not covered by the spin-on hard mask, andafter the glass has been etched away the blocking material is alsoremoved. A highly concentrated p-type doped glass is then applied overthe entire fin and substrate. The p-type glass 710 will allow the fin tobe doped as a p-type material to build the p-channel.

In FIGS. 39 and 40 the substrate, fin, and glass have been annealed.This drives dopants in from the glass into the silicon material. Theglass is then removed using, for example, an oxide etch to leave thestructure shown in FIGS. 39 and 40. This structure has a siliconsubstrate at its base and an n-doped well at the top of the substrate712. In addition, the fin has a lower portion 714 that is also n-dopedto form the back gate. The fin has an upper portion 716 which is p-dopedto form the current flow channel.

In FIGS. 41 and 42 the entire structure is covered with an oxide layer718, such as silicon dioxide or another oxide. The oxide forms anisolation oxide which is then planarized to a determined level as shownin FIGS. 43 and 44 to expose a certain portion of the fin. The oxide isremoved away to expose a portion of the part of the fin that is n-doped714. As shown in FIGS. 43 and 44 the fin is exposed so that the entirep-channel is exposed as is a portion of the N doped back gate 714. Acontrol gate 720 may then be formed around the entire exposed area ofthe fin down to the level of the oxide. The height or level of the oxideaccordingly determines the size of the control gate. The control gate isdeeper than the p-channel and covers the entire active fin height.

The control gates are typically metal and may be formed in any of avariety of different ways. In the illustrated example, the control gatesare formed first by polysilicon patterning to build a structurecorresponding to the desired shape 720 of the control gates. After thepatterning is completed at this level the polysilicon is then removedleaving a void in the shape of the desired control gate. The void isthen back filled with metal to form the control gate. Electrodes andother connectors may then be attached to the metal. In the illustratedexample there are two control gates however there may be one or nocontrol gates depending upon the intended final form of the JFET.

In FIGS. 45 and 46 a residual spacer has been applied to the fin tocontrol subsequent epitaxial growth. The spacer 722 is applied aroundthe base of the fin over the oxide layer which remains in place.

FIGS. 47 to 55 are cross-sectional side and front view diagrams ofstages of further fabrication of the device of FIG. 29. In these figuressource, gate, and drain are added. The cross-sectional front view ofFIGS. 48, 51, and 54 are taken at the position of the source which issimilar to the view at the drain. The front cross-sectional view ofFIGS. 49, 52, and 55 are taken at the position of the gate, rather thanat the position of the control gate as in FIGS. 31 to 46. This isbecause the control gates, at least in polysilicon form have alreadybeen formed and are not affected by the other stages.

In FIGS. 47, 48, and 49 the source gate and drain of the JFET have beenformed. The source 730 and drain 732 are formed by epitaxial growth of ap-type element and the gate 734 is formed by n-type epitaxial growth.The source and drain are formed over the fin and the spacer usingpatterning and epitaxial growth. The source and drain are prevented bythe spacer 722 from coming into contact with or coming too close to thedeep n-well or back gate 714 of the fin. As a result, each contact nodemakes contact only with the p-channel. The source and drain can beformed by applying a doped material over the p-channel or by doping theactual p-channel. Similarly, the n-type gate is formed in the fin orover the fin and is blocked by the has spacer 722 from coming too closeto the n-type back gate. On the other hand, as shown in FIG. 22 forexample the control gate wraps all the way around the p-channel and isphysically contacting the n-type back gate.

As illustrated a first control gate is between and in contact with thesource and the gate and the second control gate is between and incontact with the gate and the drain. As shown, an isolation barrier isapplied over and surrounding the control gates to prevent conduction andelectrical contact between the control gates and the source, gate, anddrain. The control gates may be isolated with any of variety ofdielectric barriers and may also be physically spaced apart from anyother structure.

In FIGS. 50, 51, and 52 the entire structure is covered in a deep layerof isolation oxide 738 this isolates the source, gate, and drain as wellas the control gates from each other. The top layer of the isolationoxide may be planarized using any of a variety of different processes tobe, for example, at the level of the top of the control gates,electrodes and other structures. The fin, together with the source,gate, and drain are well below the isolation oxide in this example.

In FIGS. 53, 54, and 55 contacts are formed over the gates, thesecontacts 740, 742 and 744 allow connections to be made to the source,gate, and drain of the transistor device. In addition, the polysiliconcontrol gates may be dissolved and backfilled with metal depending uponthe particular implementation for the control gates. The top layer ofdielectric 738 may be used as an interlayer dielectric in the event thatadditional components are to be formed over the JFET structure. Theelectrodes may be formed of any of a variety of different materialsdepending on the fabrication technology including tungsten.

As described, a very common and widely used transistor type (NET) may beused in a SoC, power application, or other type of IC that is fabricatedusing a non-planar transistor process technology. Furthermore, theresistor or JFET device provides unique FinFET transport characteristicsthat are not seen in as planar fabrication technology.

FIG. 55 illustrates a computing device 100 in accordance with oneimplementation of the invention. The computing device 100 houses asystem board 2. The board 2 may include a number of components,including but not limited to a processor 4 and at least onecommunication package 6. The communication package is coupled to one ormore antennas 16. The processor 4 is physically and electrically coupledto the board 2. In some implementations of the invention, any one ormore of the components, controllers, hubs, or interfaces are constructedusing a FinFET architecture that includes solid source-diffusedjunctions.

Depending on its applications, computing device 100 may include othercomponents that may or may not be physically and electrically coupled tothe board 2. These other components include, but are not limited to,volatile memory (e.g., DRAM) 8, non-volatile memory (e.g., ROM) 9, flashmemory (not shown), a graphics processor 12, a digital signal processor(not shown), a crypto processor (not shown), a chipset 14, an antenna16, a display 18 such as a touchscreen display, a touchscreen controller20, a battery 22, an audio codec (not shown), a video codec (not shown),a power amplifier 24, a global positioning system (GPS) device 26, acompass 28, an accelerometer (not shown), a gyroscope (not shown), aspeaker 30, a camera 32, and a mass storage device (such as hard diskdrive) 10, compact disk (CD) (not shown), digital versatile disk (DVD)(not shown), and so forth). These components may be connected to thesystem hoard 2, mounted to the system board, or combined with any of theother components.

The communication package 6 enables wireless and/or wired communicationsfor the transfer of data to and from the computing device 100. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication package 6 may implementany of a number of wireless or wired standards or protocols, includingbut not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+,HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, Ethernetderivatives thereof, as well as any other wireless and wired protocolsthat are designated as 3G, 4G, 5G, and beyond. The computing device 100may include a plurality of communication packages 6. For instance, afirst communication package 6 may be dedicated to shorter range wirelesscommunications such as Wi-Fi and Bluetooth and a second communicationpackage 6 may be dedicated to longer range wireless communications suchas GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.

The processor 4 of the computing device 100 includes an integratedcircuit die packaged within the processor 4. The term “processor” mayrefer to any device or portion of a device that processes electronicdata from registers and/or memory to transform that electronic data intoother electronic data that may be stored in registers and/or memory.

In various implementations, the computing device 100 may be a laptop, anetbook, notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. The computing device may be fixed,portable, or wearable. In further implementations, the computing device100 may be any other electronic device that processes data.

Embodiments may be implemented as a part of one or more memory chips,controllers, CPUs (Central Processing Unit), microchips or integratedcircuits interconnected using a motherboard, an application specificintegrated circuit (ASIC), and/or a field programmable gate array(FPGA).

References to “one embodiment”, “an embodiment”, “example embodiment”,“various embodiments”, etc., indicate that the embodiment(s) of theinvention so described may include particular features, structures, orcharacteristics, but not every embodiment necessarily includes theparticular features, structures, or characteristics. Further, someembodiments may have some, all, or none of the features described forother embodiments.

In the following description and claims, the term “coupled” along withits derivatives, may be used. “Coupled” is used to indicate that two ormore elements co-operate or interact with each other, but they may ormay not have intervening physical or electrical components between them.

As used in the claims, unless otherwise specified, the use of theordinal adjectives “first”, is “second”, “third”, etc., to describe acommon element, merely indicate that different instances of likeelements are being referred to, and are not intended to imply that theelements so described must be in a given sequence, either temporally,spatially, in ranking, or in any other manner.

The drawings and the forgoing description give examples of embodiments.Those skilled in the art will appreciate that one or more of thedescribed elements may well be combined into a single functionalelement. Alternatively, certain elements may be split into multiplefunctional elements. Elements from one embodiment may be added toanother embodiment. For example, orders of processes described hereinmay be changed and are not limited to the manner described herein.Moreover, the actions of any flow diagram need not be implemented in theorder shown; nor do all of the acts necessarily need to be performed.Also, those acts that are not dependent on other acts may be performedin parallel with the other acts. The scope of embodiments is by no meanslimited by these specific examples. Numerous variations, whetherexplicitly given in the specification or not, such as differences instructure, dimension, and use of material, are possible. The scope ofembodiments is at least as broad as given by the following claims.

The following examples pertain to further embodiments. The variousfeatures of the different embodiments may be variously combined withsome features included and others excluded to suit a variety ofdifferent applications. Some embodiments pertain to a method includingforming a fin on a substrate, depositing a glass of a first dopant typeover the substrate and over a lower portion of the fin, depositing aglass of a second dopant type over the substrate and the fin, annealingthe glass to drive the dopants into the fin and the substrate, removingthe glass, and forming a first and a second contact over the fin withoutcontacting the lower portion of the fin.

Further embodiments include forming a control gate over the fin, thecontrol gate being a conductive material over the top and on the sidesof the fin to control current flow through the fin between the first andsecond contacts.

In further embodiments, forming a control gate comprises patterningpolysilicon over the fin, removing the polysilicon and backfilling thevoid from the polysilicon with metal Forming a control gate comprisesforming a control gate over the fin after removing the glass and beforeforming the first and second contacts. The first contact comprises asource, the second contact comprises a drain, the method furthercomprising forming a gate over the fin between the source and the drainwithout contacting the lower portion of the fin.

Further embodiments include depositing an oxide over the siliconsubstrate after removing the glass, the oxide having a depth to coverthe lower portion of the fin, the oxide isolating the lower portion ofthe fin before forming the doped source, gate, and drain.

Further embodiments include forming an isolation spacer over the lowerportion of the fin before forming the source, gate, and drain to preventthe source, gate, and drain from contacting the lower portion of thefin.

In further embodiments, the substrate and the fin are silicon.

In further embodiments depositing a glass of a first dopant typeincludes depositing the glass of the first dopant type over thesubstrate and the fin, depositing a blocking material (carbon hard mask)over the substrate and a portion of the fin, removing the depositedglass that is not covered in the blocking material, and removing theblocking material.

In further embodiments the blocking material is a carbon hard mask.Depositing glass of a second dopant type comprises removing the glass ofthe first dopant type from a portion of the fin and depositing the glassof the second dopant type over the portion of the fin and over the glassof the first dopant type. Removing the glass comprises removing theglass using an oxide etcher.

Further embodiments include forming a control gate over the fin, thecontrol gate being a conductive material over the top and on the sidesof the fin to control current flow through the fin between the sourceand the drain.

In further embodiments, forming a control gate comprises patterningpolysilicon over the fin, removing the polysilicon and backfilling thevoid from the polysilicon with metal. Forming a control gate comprisesforming a control gate over the fin after removing the glass and beforeforming the source, gate, and drain.

Some embodiments pertain to an apparatus including a substrate, a finabove the substrate, the fin having a channel of a first dopant type andat least a portion of a well of a second dopant type, and a firstcontact and a second contact of the fin formed without contacting thewell of the fin;

Further embodiments include a control gate between the first and secondcontact formed over and around the fin to control resistance between thefirst and the second contact.

In further embodiments, the control gate is metal. The control gate isformed of polysilicon which is then removed and a void caused byremoving the polysilicon is filled with metal. The first and the secondcontacts are formed of the first dopant type. The first and secondcontacts are formed over the fin of epitaxial growth. The first andsecond contacts are formed in the fin of a dopant in the fin. Thechannel of the first dopant type is a current channel between the firstand second contacts. The control gate extends over and around thechannel of the fin on two sides.

In further embodiments, the first contact comprises a source and thesecond contact comprises a drain, the apparatus further comprising agate of the second dopant type formed of the fin between the source andthe drain formed without contacting the well of the fin.

In further embodiments, the gate is formed over the fin of epitaxialgrowth. The gate is formed in the fin of a dopant in the fin. The gateis formed in the fin by depositing a doped glass over the fin, annealingthe glass, and removing the glass. The channel of the first dopant typeis a current channel between the source and the drain and wherein avoltage applied to the gate determines whether current flows in thechannel.

Further embodiments include a control gate between the source and thedrain, the control gate extending over and around the channel of the finon two sides and being configured to restrict current flow through thechannel.

In further embodiments, the control gate is between the source and thegate, the transistor further comprising a second control gate betweenthe gate and the drain. The control gate is metal. The control gate isformed of polysilicon which is then removed and a void caused byremoving the polysilicon is filled with metal.

Some embodiments pertain to a computing system including a communicationchip, a power supply and a processor having a plurality of transistors,at least one transistor being a junction gate field effect transistorhaving a substrate, a fin above the substrate, the fin having a channelof a first dopant type and at least a portion of a well of as seconddopant type, a source and a drain of the first dopant type of the finformed without contacting the well of the fin, and a gate of the seconddopant type formed of the fin between the source and the drain formedwithout contacting the well of the fin.

In further embodiments, the gate is formed in the fin by depositing adoped glass over the fin, annealing the glass, and removing the glass.The junction gate field effect transistor further includes a controlgate between the source and the gate, the control gate being formed overand around the fin to control resistance between the source and thedrain. The control gate is formed by patterning polysilicon over thefin, removing the polysilicon and backfilling the void from thepolysilicon with metal.

Some embodiments pertain to a junction gate field effect transistorincluding a substrate, a fin above the substrate, the fin having achannel of a first dopant type and at least a portion of a well of asecond dopant type, a source and a drain of the first dopant type of thefin formed without contacting the well of the fin, and a gate of thesecond dopant type formed of the fin between the source and the drainformed without contacting the well of the fin.

Some embodiments pertain to a variable resistor including a substrate, afin above the substrate, the fin having a channel of a first dopant typeand at least a portion of a well of a second dopant type, a firstcontact and a second contact of the fin formed without contacting thewell of the fin, and a control gate between the first and second contactformed over and around the fin to control resistance between the firstand the second contact.

What is claimed is:
 1. An apparatus comprising: a substrate; a fin abovethe substrate, the fin having a channel of a first dopant type and atleast a portion of a well of a second dopant type; a first sourcecontact and a second drain contact of the fin of a first dopant typeformed without contacting the well of the fin; and a gate of the seconddopant type formed of the fin between the source and the drain formedwithout contacting the well of the fin.
 2. The apparatus of claim 1,further comprising a control gate between the first and second contactformed over and around the fin to control resistance between the firstand the second contact.
 3. The apparatus of claim 1, wherein the firstand second contacts comprise a dopant in the fin.
 4. The apparatus ofclaim 2, wherein the control gate extends over and around the channel ofthe fin on two sides.
 5. The apparatus of claim 1, wherein the gate isover the fin of epitaxial growth.
 6. The apparatus of claim 1, whereinthe channel of the first dopant type is a current channel between thesource contact and the drain contact and wherein a voltage applied tothe gate determines whether current flows in the channel.
 7. Theapparatus of claim 1, further comprising a control gate between thesource and the drain, the control gate extending over and around thechannel of the fin on two sides and being configured to restrict currentflow through the channel.
 8. A computing system comprising: acommunication chip; a power supply; and a processor having a pluralityof transistors, at least one transistor being a junction gate fieldeffect transistor having a substrate, a fin above the substrate, the finhaving a channel of a first dopant type and at least a portion of a wellof a second dopant type, a source and a drain of the first dopant typeof the fin formed without contacting the well of the fin, and a gate ofthe second dopant type formed of the fin between the source and thedrain formed without contacting the well of the fin.
 9. The computingsystem of claim 8, wherein the gate is formed in the fin by depositing adoped glass over the fin, annealing the glass, and removing the glass.10. The computing system of claim 8, wherein the junction gate fieldeffect transistor further includes a control gate between the source andthe gate, the control gate being formed over and around the fin tocontrol resistance between the source and the drain.
 11. The computingsystem of claim 10, wherein the control gate is formed by patterningpolysilicon over the fin, removing the polysilicon and backfilling thevoid from the polysilicon with metal.
 12. The computing system of claim10, wherein the source and the drain comprise dopants in the fin. 13.The computing system of claim 10, further comprising further comprisinga control gate between the source and the drain, the control gateextending over and around the channel of the fin on two sides and beingconfigured to restrict current flow through the channel.
 14. Anapparatus comprising: a substrate; a fin above the substrate, the finhaving a channel of a first dopant type and at least a portion of a wellof a second dopant type; a source contact and a drain contact of the finof a first dopant type formed without contacting the well of the fin;and a gate of the second dopant type formed of the fin between thesource and the drain, wherein the channel of the first dopant type is acurrent channel between the source contact and the drain contact andwherein a voltage applied to the gate determines whether current flowsin the channel.
 15. The apparatus of claim 14, wherein the gate isformed over and around the fin on two sides to control resistancebetween the source and the drain contact.
 16. The apparatus of claim 14,wherein the source and the drain contacts comprise a dopant in the fin.17. The apparatus of claim 14, further comprising a control gate betweenthe source contact and the drain contact, the control gate extendingover and around the channel of the fin on two sides and being configuredto restrict current flow through the channel.
 18. The apparatus of claim17, wherein source and the drain contact and the control gate comprise ajunction gate field effect transistor, wherein the source and the draincontact and the control gate do not contact the well of the fin.
 19. Theapparatus of claim 17, wherein the control gate is formed by patterningpolysilicon over the fin, removing the polysilicon and backfilling thevoid from the polysilicon with metal.
 20. The apparatus claim 14,wherein the gate is formed in the fin by depositing a doped glass overthe fin, annealing the glass, and removing the glass.